Cooling means for incased electrical apparatus



Get. 28, 1930.

E. L. R. BLISS 1,780,110

COOLING MEANS FOR INCASED ELECTRICAL APPARATUS Filed Jan. 5, 1929 Inve nto r- 664, His Axtorney.

Patented Get. 28, 1930 UNlTiEfi STATES PATEAT EDWIN L. R. BLISS, C-F LANESBORO, llZASSACI-IUSETTS. ASSIGNOE TO GENERAL ELECTRIC CQIVIPANY, A CGBE ORATION NEW YORK COOLING MEANS F93 INGASED ELECTRICAL APPARATUS Application filed January 5, 1829.

My invention relates to cooling means for incased electrical apparatus and more particularly to transformers and other forms of electrical apparatus which are immersed in an insulating liquid within a suitable casing. The losses in sucn apparatus appear a neat and the maximum safe load is limited by the temperature rise due to this heat. Lt is customary to provide the apparatus cas ings with external radiators through which the insulating liquid may flow and be cooled, thus increasing the safe maximum load by increasing the rate at which the heat is dissipated. The insulatin liquid which is usually used is a specially prepared oil having high diel ctric strength. To maintain its high dielectric strength, the oil must be kept free from any appreciable amount of moisture and it should, as far as possible, be kept out of contact with oxygen, particularly when at a high temperature. The general object of the invention is to provide a completely sealed electrical apparatus casing containing insulating liquid and having an improved form of expansible external heat radiator both to cool the liquid and to permit its expansion and contraction under varying temperatures without contact with the surrounding air.

The invention will be better understood from the following description taken in connection with the accompanying drawing in which Fig. 1 shows a casing for an oil im mersed transtormer having external heat adiating tubes constructed in accordance with the invention, Fig. shows a casing for an oil immersed traistormer having another form of external tubular heat radiator, Fig. 3 shows a detail of construction, and Fig. 4: is an enlarged sectional view on the lines l i of Figs. 2 and 3.

The invention is shown in Fig. 1 in connection with an incased oil immersed transformer, the casing 10 of the transtorn'ier being provided with a plurality of external vertical heat radiating tubes 11 communicating at their upper and lower portions of the casing. The oil absorbs heat from the transformer and rises by convection inside the casing, returning through the tubes 11 where Serial IEO. 330,634.

it is cooled. The casing 10 may be completely filled with oil or there maybe a space above the oil filled with gas, an inert gas being preferably used and the oil level being at least high enough to permit the oil to How freely into the upper ends of the tubes 11.

The casing 10 is completely scaled from communication with the outside air so that none of the air with its moisture and oxygen can reach the oil to contaminate it. The oil. however, must expand and contact as its temperature changes, its volume being considerably more when hot than when cold. These changes in volume of the oil between no load and tall load conditions ot' the apparatus are made possible without rupturing the casing or tubes by making the tubes expansihle to hold any surplus oil forced out of the casmg.

The tubes 11 have flexible walls which ar non-circular in cross section, thin tlexibl sheetsteel being a suitable material from which the walls may be made. When the temperature of the oil in the casing 10 increases, it expands and some of it is torccd into the tubes ll. This increases the pressure in the tubes and torccstheir walls into a more nearly circular cross sectional uhape so that their capacity is increased to receive the surplus oil from the casing 10. There is always a tendency of the tubes 11 to return to their normal non-circular shape and force oil hack into the casing 10 whenever the oil in the casing cools and contracts, the normal amount of oil being thus substantially maintained at all times in the casing.

The lower end of one of the tubes 11 with an elbow 1? connecting it to the casing 10 is shown in Fig. 3. This tube has a cross sectional shape, more clearly shown in Fig; l, which has been found to giv good results. The tube has enlarged smoothly curved edge portions 13 merging gradually into smoothly curved spaced normally re-entrant side portions 14 so that the tube is non-circular in cross section but has no sharp angles or corners.

Under no load conditions with the oil at the lowest temperature usual under these conditions, the re-entrant side portions of. the

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tubes should be spaced somewhat as shown in full lines in Fig. l and at the same time the tube walls should be strong enough to overcome the pressure of the oil. This will prevent any air being drawn into the casing in case of leakage near the top of the casing.v When the oil is heated and expanded, thetubes will expand under the increased internalpressurc of the oil, the

' side portions ll of the tubes separating toward the positions indicated by the dotted lines of Fig. a. ll the oil occasionally reaches an unusually low temperature, the tubes may contract beyond the condition. shown in full lines in Fig. 4-, their side portions 1% approaching thepositions indicated by the dotted lines '16;

Another arrangement of expansible tubes which may be used in accordance with the invention is shown in Fig. 2. The tubes 11 as shown in this figure are connected in groups between top and bottom headers 17 iich communicate by pipe connections 18 with the upper and lower portions of the casing 10. The cross sectional shapes of these tubes maybe the same as has already been described in connection with the tubes 11 of Fig. 1. Whatever the particulararrangement or cross-sectional shape of the tubes may be, a sufiicient number of tubes u should be used to provide the necessary change in volume required by the thermal expansion and contraction of the oil. It desired, some form of pressure relief device,

such as the usual form of pressure relief pipe 19 sealed at the outer end by a rupturable diaphragm, may be provided to relieve any very sudden or excessive increase of pressure within the casing 10.

The invention hasbeen explained by describing and illustrating certain particular forms thereof but it will be apparent that various changes may be made without departing from the scope or the invention as defined in the appended claims.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination with a casing for elec-.

' trical apparatus immersed in an insulating liquid within said casing, the casing being completely sealed from communlcation with the outside air, ot heat radiating tubes filled 'with' insulating liquid and connected to the upper and lower portions of said casing, whereby said liquid may flow through sald tubes to be cooled, said tubes being expansible to permit thermal eXpansion and con- "traction of said liquid between no load and full load conditions of said apparatus.

2. The combmatlon witha casing for electrical apparatus immersed in an insulating liquid within said casing, the casing being' upper and lower portions of said casing,

whereby said liquid may flow through said tubes to be cooled, said tubes having flexible walls of non-circular cross-sectional shape the outside air, of heat radiating tubes filled j with insulating liquid and connected to up per and lower portions of said casing, whereby said liquid may fiow through said tubes to be cooled said tubes having flexible walls with enlarged edge portions connected by reentrant side portions to permit thermal expansion and contraction of said liquid between no load and full load conditions of said apparatus.

4. The combination with a casing fcr'electrical apparatus immersed in an insulating liquid within said casing the casing being completely sealed from communication with the outside air, of heat radiating tubes filled with insulating liquid and connected to the upper and lower portions of said casing, w iereby said liquid may flow through said tubes to be cooled, said tubes having flexible walls withenlarged smoothly curved 

